Simulation Studies of Thin Heavy Oil Reservoirs

Heavy oil production from extremely viscous reservoirs requires thermal production techniques, such as Steam Assisted Gravity Drainage (SAGD). This report deals with the first step in expanding/developing alterations to the SAGD process – quantifying the impact of problematic reservoir characteristics (thin oil columns and gas zones) on production performance to try to gain insight into the best avenue for improvement. For all oil column thickness studied, only reservoirs with an aspect ratio (AR) – ratio of well pair spacing (horizontal distance between adjacent wells) to reservoir thickness – of 4:1 or less are economic. For each case, the optimum AR is 2:1. The presence of a gas zone overlying a thin reservoir is detrimental to SAGD efficiency regardless of gas zone volume. The presence of a gas zone does not change the choice of optimum aspect ratio (2:1) or the largest aspect ratio (4:1) for which SAGD operations will be economic. Additionally, it is shown that the sink/source well model is not sufficient to capture early steam chamber growth and production behavior.